This project examines effects of LHRH antagonist in man. Most recently, we gave a GnRH antagonist and testosterone to normal men in a protocol simulating a prototype of a likely male contraceptive regimen. Sperm counts started declining on week 4 and complete azoospermia was reached in 7 of 8 subjects. in the 8th man total sperm count decreased to a nadir of 1.4 million and residual sperm showed no motility and viability. No systemic or significant local side effects were observed other than a small reaction at the injection